Conveyor idler with locking device for preventing reverse rotation

ABSTRACT

A conveyor idler includes a drum having an outer surface and an inner surface, a shaft ( 24 ) about which the drum can rotate in a forward direction, a locking mechanism for preventing the drum from rotating in a reverse direction (R) but which locking mechanism permits rotation of the drum in the forward direction, the locking mechanism having at least one wedging surface ( 44 ) fixed directly or indirectly to the drum, and a locking member ( 38 ) interposed between the wedging surface and the shaft, the locking member being rotatable about the shaft when the drum rotates in the forward direction, but when an attempt is made to rotate the drum in the reverse direction the locking member becomes releasably wedged between the wedging surface and the shaft, or a surface fixed to the shaft, thereby preventing the drum from rotating in the reverse direction.

FIELD OF THE INVENTION

This invention relates to a conveyor idler which can rotate in onedirection only.

BACKGROUND TO THE INVENTION

International patent application PCT/IB00/01571 published under WO01/32537A1 describes a conveyor idler with a braking mechanism withinthe drum of the conveyor idler. The braking mechanism permits the drumto rotate in a forward direction but not in a reverse direction. Thebraking mechanism consists of a brake guide fixed to the shaft of theconveyor idler. The brake guide has recesses on its circumference. Oneach of the recesses a ball bearing is located. One of the ball bearingsbecomes wedged between the inner surface of the drum and its recess onthe brake guide when an attempt is made to rotate the drum in thereverse direction thereby preventing the drum from being rotated in thereverse direction. The conveyor idler suffers from the disadvantage thatgenerally only one of the ball bearings becomes wedged between the drumand the brake guide and therefore that all the locking torque istransferred through only one ball bearing. In addition, the brake guideis relatively large and the ball bearings contact the drum even when itrotates in the forward direction. This contact results in the generationof noise and in wear.

SUMMARY OF THE INVENTION

According to the invention a conveyor idler includes a drum having anouter surface and an inner surface, a shaft about which the drum canrotate in a forward direction, a locking mechanism for preventing thedrum from rotating in a reverse direction but which locking mechanismpermits rotation of the drum in the forward direction, the lockingmechanism having at least one wedging surface fixed directly orindirectly to the drum, and a locking member interposed between thewedging surface and the shaft, the locking member being rotatable aboutthe shaft when the drum rotates in the forward direction, but when anattempt is made to rotate the drum in the reverse direction the lockingmember becomes releasably wedged between the wedging surface and theshaft or a surface fixed to the shaft thereby preventing the drum fromrotating in the reverse direction.

A plurality of wedging surfaces may be provided with a locking memberbeing provided between each wedging surface and the shaft.

The plurality of locking members are preferably connected together byconnecting means. The connecting means may be a locking housing havingcircumferentially spaced cages for the locking members.

Each locking member is preferably rotatably located within its cage.Each locking member is preferably also radially movable within its cage.

The locking housing may consist of two axially spaced end members, withthe cages being formed between the end members and between pairs ofspaced axially extending walls located between the end members.

The cages preferably extend radially outwardly beyond the circumferenceof the end members.

A reinforcing web may extend between the end members.

The wedging surface preferably includes a ramp. The wedging surfacepreferably forms part of, or is fixed to, an end cap or closure of thesleeve, the end cap or closure being fixed to the drum. The wedgingsurface may be located within a locking housing receptacle which isfixed to the end cap. The locking housing receptacle may include aplurality of circumferentially spaced slots which engage a plurality ofradially extending webs in the end cap thereby to fix the lockinghousing receptacle to the end cap.

In another embodiment of the invention the wedging surface may belocated within a locking housing receptacle which is fixed to the innersurface of the sleeve.

The locking member may be a ball bearing or roller bearing.

According to another aspect of the invention a locking mechanism for aconveyor idler for releasably locking a drum of the conveyor idler fromrotating about a shaft in a reverse direction but which permits rotationof the drum in a forward direction about the shaft, the lockingmechanism includes a connecting means connecting a plurality ofcircumferentially spaced locking members together which locking membersare in use located between wedging surfaces fixed to the drum so that inuse when an attempt is made to rotate the drum in the reverse direction,the locking members will simultaneously become releasably wedged betweenthe shaft and the wedging surfaces thereby preventing the drum frombeing rotated in the reverse direction.

The connecting means preferably include a cage for each locking member.

Each locking member is preferably rotatable within its cage. Eachlocking member is preferably also radially moveable within its cage.

The locking housing may consist of two axially spaced end members, withthe cages being formed between the end members and between pairs ofspaced axially extending walls located between the end members. Thecages may extend radially outwardly beyond the circumference of the endmembers. A reinforcing web may extend between the end members.

The locking mechanism may include a receptacle for the locking membersand their connecting means, the receptacle containing the wedgingsurfaces and having fixing means for fixing the receptacle directly orindirectly to the drum.

The fixing means may comprise a plurality of spaced slots for engaging aplurality of radially extending webs in an end cap of the conveyoridler.

According to another aspect of the invention an end cap for a conveyoridler includes a receptacle for a plurality of circumferentially spacedlocking members, the receptacle having a wedging surface for eachlocking member so that in use a drum of the conveyor idler to which theend cap is fixed can rotate in a forward direction but not in a reversedirection because the locking members become releasably wedged betweentheir wedging surfaces and a shaft of the conveyor idler.

The receptacle may be integrally formed with the end cap. Alternatively,the receptacle may be located within a separate housing which is fixedto the end cap. The separate housing may include a plurality ofcircumferentially spaced slots which engage a plurality of radiallyextending webs in the end cap to fix the separate housing to the endcap.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of one end of a conveyor idleraccording to the invention;

FIG. 2 is a perspective view of a locking housing;

FIG. 3 is a plan view of the locking housing with its rollers displacedradially outwardly;

FIG. 4 is the same view as FIG. 3 but with the rollers displacedradially inwardly;

FIG. 5 is a perspective view from the inside of an end cap of the idlerroller;

FIG. 6 is a perspective view from the outside of the end cap;

FIG. 7 is an end view of an end cap containing the locking housing inits unlocked position;

FIG. 8 is the same view as FIG. 7 but with the locking housing in itslocked position;

FIG. 9 is a cross-sectional view on line II-II of FIG. 1 in an unlockedposition;

FIG. 10 is the same view as FIG. 9 but in a locked position;

FIG. 11 is an exploded perspective view of an end cap according toanother embodiment of the invention;

FIG. 12 is an assembled cross-sectional view of the end cap of FIG. 11;

FIG. 13 is a perspective view from the outside of the locking housingreceptacle of the end cap of FIG. 11; and

FIG. 14 is a cross-sectional view of a conveyor idler according toanother embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring firstly to FIG. 1, a conveyor idler 10 has a drum 12 with apair of end caps 14 of which only one is shown. The end caps 14 arewelded by welds 16 to the drum 12. The drum 12 is also known as a sleeveor shell.

The drum 12 has an outer surface 18 over which a conveyor belt (notshown) can run. Each end cap 14 has a bearing housing 20 for a bearing22 which enables a shaft 24 to rotate relative to the end cap 14 andhence relative to the drum 12. A labyrinth seal 26 protects the bearing22 from the ingress of foreign matter.

A locking housing 28 is located between the end cap 14 and the shaft 24.It will be appreciated that a locking housing 28 can be located in oneor both of the end caps 14.

Referring now to FIGS. 2 to 4, the locking housing 28 consists of twoaxially spaced members in the form of rings 32 with four pairs of spacedwalls 34 extending between the rings 32 to define four cages 36 forrollers 38. The cages 36 project radially outwardly from the rings 32. Areinforcing web 39 extends between the rings 32. The rollers 38 canrotate within their cages 36 and can also move radially within theircages 36 as can be seen from FIGS. 3 and 4.

Referring now to FIGS. 5 and 6, the end cap 14 has a locking housingreceiving zone 40. This zone 40 has four recesses 42 each with a ramp44. Conveniently the end cap 14 is a pressing or a moulding. However thelocking housing receiving zone 40 may be manufactured separately to theend cap 14 and subsequently secured to the end cap 14.

In FIGS. 7 and 8 the locking housing 28 is shown in its unlocked andlocked positions respectively in the end cap 14. How the locking housing28 moves between these two positions is described with reference toFIGS. 9 and 10. Referring in this regard firstly to FIG. 9, when thedrum 12, and hence the end cap 14, rotate in the direction of arrow F,the locking housing 28 is located in the position shown with its rollers38 at the back of their ramps 44 and out of engagement with the shaft24. However when the drum 12, and hence the end cap 14, attempt torotate in the direction of arrow R as shown in FIG. 10, the lockinghousing 28 moves relative to the end cap 14 to the position shown whichis the locked position. In this locked position the rollers 38 havemoved up their ramps 44 to become releasably wedged between their ramps44 and the shaft 24 to lock the end caps 14 and hence the drum 12, tothe shaft 24 thereby to prevent rotation of the drum 12 relative to theshaft 24. Once the direction of rotation is reversed back to that shownin FIG. 9, the rollers 38 move down their ramps 44 out of engagementwith the shaft 24 enabling the end cap 14 and hence the drum 12 torotate relative to the shaft 24 again.

The locking housing 28 ensures that the circumferential spacing betweenrollers 38 does not vary, and therefore that all four rollers 38 willsimultaneously engage the shaft 24 when an attempt is made to reversethe direction of rotation of the drum 12. This has the advantage thatthe locking torque is shared equally between the four rollers 38.Referring now to FIG. 11 and 12 a nylon end cap 14.1 includes a bearinghousing 20.1 and a locking housing receptacle 48 which has a lockinghousing receiving zone 40.1 and a lip 50 with circumferentially spacedslots 52. The end cap 14.1 has radially extending ribs 46. The spacingbetween the slots 52 is the same as that between the extremities of theribs 46 so that the ribs 46 can locate within the slots 52 rotatably tolock the locking housing receptacle 48 to the end cap 14.1.

The locking housing receiving zone 40.1 is formed of mild steel and isan insert in the nylon locking housing receptacle 48. It will however beappreciated that the locking housing receiving zone 40.1 could be madeof nylon and thus be integrally moulded with the locking housing support48.

A seal 54 is provided in a groove 56 in the locking housing receptacle48. The seal 54 prevents the ingress of foreign matter to the end cap14.1 and the locking housing 28.

In use, when an attempt is made to rotate the conveyor idler drum 12.1of the conveyor idler 10.1, into which the end cap 14.1 is a press fit,in the reverse direction the rollers 38 simultaneously wedge betweentheir ramps 44.1, and lock the drum 12.1 from rotating in the reversedirection. The locking torque is transmitted from the shaft 24.1, whichcannot rotate, through the rollers 38, through the locking housingreceptacle 48, to the drum 12.1.

Although the locking housing receptacle 48 is shown fixed to the end cap14.1 and located inside the drum 12, the locking housing receptacle 48could be fixed directly to the drum 12 or, for example, via webs (notshown) extending radially inwardly from the inner surface of the drum 12of the conveyor idler and the locking housing receptacle 48 could alsobe located outside the drum 12.

Referring now to FIG. 14 a conveyor idler 110 is shown which is suitablefor lighter-weight applications. The idler 110 includes a drum 112 whichis rotatable on bearings 122 about a shaft 124. The shaft 124 is held inend sockets 125 which are mountable to a conveyor frame (notillustrated). The end sockets 125 are fixed to the shaft. A lockinghousing 130 is fixed to end caps 114 (only one of which is shown). Itwill be appreciated that the rollers (not shown) of the locking housing130 become wedged between the surface of the end socket 125 and theirwedging surfaces (not shown). The end caps are formed from a plasticsmaterial and are sized to form a friction fit with the conveyor drum112. Seals 126 prevent the ingress of dirt and other undesirablesubstances into the bearing housings containing the bearings 122.

It will be appreciated that many modifications or variations of theinvention are possible without departing from the spirit or scope of theinvention.

1. A conveyor idler including a drum having an outer surface and aninner surface, a shaft about which the drum can rotate in a forwarddirection, a locking mechanism for preventing the drum from rotating ina reverse direction but which locking mechanism permits rotation of thedrum in the forward direction, the locking mechanism having at least onewedging surface fixed directly or indirectly to the drum, and a lockingmember interposed between the wedging surface and the shaft, the lockingmember being rotatable about the shaft when the drum rotates in theforward direction, but when an attempt is made to rotate the drum in thereverse direction the locking member becomes releasably wedged betweenthe wedging surface and the shaft, or a surface fixed to the shaft,thereby preventing the drum from rotating in the reverse direction. 2.The conveyor idler of claim 1 wherein a plurality of wedging surfacesare provided with a locking member being provided between each wedgingsurface and the shaft.
 3. The conveyor idler of claim 2 wherein theplurality of locking members are connected together by connecting means.4. The conveyor idler of claim 3 wherein the connecting means is alocking housing having circumferentially spaced cages for the lockingmembers.
 5. The conveyor idler of claim 4 wherein each locking member isrotatably located within its cage.
 6. The conveyor idler of claim 4wherein each locking member is radially movable within its cage.
 7. Theconveyor idler of claim 4 wherein the locking housing consists of twoaxially spaced end members, with the cages being formed between the endmembers and between pairs of spaced axially extending walls locatedbetween the end members.
 8. The conveyor idler of claim 7 wherein thecages extend radially outwardly beyond the circumference of the endmembers.
 9. The conveyor idler of claim 7 including a reinforcing webextending between the end members.
 10. The conveyor idler of claim 1wherein the wedging surface includes a ramp.
 11. The conveyor idler ofclaim 1 wherein the wedging surface forms part of, or is fixed to, anend cap or closure of the sleeve, the end cap or closure being fixed tothe drum.
 12. The conveyor idler of claim 11 wherein the wedging surfaceis located within a locking housing receptacle which is fixed to the endcap.
 13. The conveyor idler of claim 12 wherein the locking housingreceptacle includes a plurality of circumferentially spaced slots whichengage a plurality of radially extending webs in the end cap thereby tofix the locking housing receptacle to the end cap.
 14. The conveyoridler of claim 1 wherein the wedging surface is located within a lockinghousing receptacle which is fixed to the inner surface of the sleeve.15. The conveyor idler of claim 1 wherein the locking member is a ballbearing or roller bearing.
 16. A locking mechanism for a conveyor idlerfor releasably locking a drum of the conveyor idler from rotating abouta shaft in a reverse direction but which permits rotation of the drum ina forward direction about the shaft, the locking mechanism including aconnecting means connecting a plurality of circumferentially spacedlocking members together which locking members are in use locatedbetween wedging surfaces fixed to the drum so that in use when anattempt is made to rotate the drum in the reverse direction, the lockingmembers will simultaneously become releasably wedged between the shaftand the wedging surfaces thereby preventing the drum from being rotatedin the reverse direction.
 17. The locking mechanism of claim 16 whereinthe connecting means includes a cage for each locking member.
 18. Thelocking mechanism of claim 17 wherein each locking member is rotatablewithin its cage.
 19. The locking mechanism of claim 17 wherein eachlocking member is radially moveable within its cage.
 20. The lockingmechanism of claim 17 wherein the locking housing consists of twoaxially spaced end members, with the cages being formed between the endmembers and between pairs of spaced axially extending walls locatedbetween the end members.
 21. The locking mechanism of claim 20 whereinthe cages extend radially outwardly beyond the circumference of the endmembers.
 22. The locking mechanism of claim 20 including a reinforcingweb extending between the end members.
 23. The locking mechanism ofclaim 16 including a receptacle for the locking members and theirconnecting means, the receptacle containing the wedging surfaces andhaving fixing means for fixing the receptacle directly or indirectly tothe drum.
 24. The locking mechanism of claim 23 wherein the fixing meanscomprises a plurality of spaced slots for engaging a plurality ofradially extending webs in an end cap of the conveyor idler.
 25. An endcap for a conveyor idler including a receptacle for a plurality ofcircumferentially spaced locking members, the receptacle having awedging surface for each locking member so that in use a drum of theconveyor idler to which the end cap is fixed can rotate in a forwarddirection but not in a reverse direction because the locking membersbecome releasably wedged between their wedging surfaces and a shaft ofthe conveyor idler.
 26. The end cap of claim 25 wherein the receptacleis integrally formed with the end cap.
 27. The end cap of claim 25wherein the receptacle is located within a separate housing which isfixed to the end cap.
 28. The end cap of claim 27 wherein the separatehousing includes a plurality of circumferentially spaced slots whichengage a plurality of radially extending webs in the end cap to fix theseparate housing to the end cap.